The present invention is related to thermal control systems generally, and more specifically to two phase pumped loop systems.
Two phase pumped loop cooling loops are known. For example, U.S. Pat. No. 4,750,543 describes a pumped loop two-phase heat transfer system, operating at a nearly constant temperature throughout. The system includes a plurality of independently operating grooved capillary heat exchanger plates supplied with working fluid through independent flow modulation valves connected to a liquid supply line, a vapor line for collecting vapor from the heat exchangers, a condenser between the vapor and the liquid lines, and a fluid circulating pump between the condenser and the heat exchangers.
The ""543 patent requires a sensor controlled flow modulation valve to regulate the flow. This system requires elaborate controls if the device being cooled varies the amount of heat generated over time. Also, it is difficult to measure the flow rate of the system. All of these systems operate at slightly above the temperature of the cooling fluid, typically air.
An improved thermal control system is desired.
One aspect of the present invention is a heat transfer system, comprising a wick, a vacuum pump and a heat exchanger. The wick receives a condensed liquid. The wick receives heat from a heat source. The vacuum pump reduces pressure in the wick while turned on, so that at least a portion of the liquid evaporates within the wick to form a vapor that is pumped by the pump. The heat exchanger is coupled to receive the vapor from the pump. The heat exchanger rejects heat to form the condensed liquid from the vapor. The heat exchanger returns the condensed liquid to the wick.
Another aspect of the invention is a method for transferring heat, comprising the steps of: transferring heat from a heat source to a wick; reducing pressure in the wick; evaporating a liquid within the wick to form a vapor; pumping the vapor out from the wick; condensing the vapor outside of the wick to form a condensed liquid; and returning the condensed liquid to the porous wick.